Alveolar shrinkage in bronchioloalveolar carcinoma without central fibrosis

Preservation of alveolar architecture in small bronchioloalveolar carcinoma (BAC) is one of the most important factors for predicting their prognosis, alveolar shrinkage in BAC, however, has not been studied well. In ten cases of pure BAC without collapse or central fibrosis, we measured two two-dimensional (2D) parameters; side-length of the alveoli facing alveolar ducts and circumference of the alveoli forming complete circles. And we also examined three-dimensionally (3D) elastic fibers and myofibroblasts in the thick sections. In BAC, 2D parameters showed alveolar shrinkage. The elastic fibers forming the alveolar framework, including the alveolar orifice, were 3D sinuous and bent in BAC, and suggested that alveolar shrinkage cased by folding of the alveolar wall. Myofibroblasts lay transversely and longitudinally in the interstitium in BAC, intertwined with the elastic fibers. Proliferation of myofibroblasts may be of importance in alveolar wall-folding and alveolar shrinkage in BAC.